Pause only stopped the stdout reader loop; yt-dlp kept transferring at
full rate until the pipe buffer filled, consuming bandwidth while the
UI claimed the download was paused. Send SIGSTOP/SIGCONT to the whole
process group (yt-dlp and its ffmpeg children) on Unix. Windows has no
equivalent signal; the limitation is documented in the helper.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Jaroslav Beneš
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